epoll is a horrible API, which has grown from the even worse select and poll API. I believe its entrenchment, despite existence of APIs like IOCP, is one of the failings of Linux, which even has negatively influenced programming languages (I am looking at you Rust). Others have already posted the "fundamentally broken" article, but to add an anecdote, after closely working with io-uring, I simply can not go back to the horrors of epoll and I wish we, as an industry, will migrate from it as soon as possible.